Methods and apparatus for borehole drilling



Aug. 19, 1969 u F,WH|YT1'| E. l l l 3,461,978l

l METHODS AND APPARATUS noaon'w nmnmuc i l 'med Apri; 2a;- 1967: l s sheets-sheet' 1 1 [inventor 5m FRANK 2m-rms B u v la" tlorfn METHODS AND APPARATUS FOR BOREHOLE DRILLING I ,5 Sheetsr-Sheet 5 Filed prix ze. 1967 nvenfor gn8. FRAM Manni? Aug@ 19, 1969 F. wHmLE 3,461,976

v v METHODS AND APP ARATUS Foa BOR/61101131111111111116 med 11pm 26. 1967 s sheets-sheet 4 'inventor l 3112 fmmg wH-nrlTL-E" United States Patent O U.S. Cl. 175-27 6 Claims ABSTRACT F THE DISCLOSURE An apparatus for use in drilling boreholes has a drawworks provided with a braking means. A fastline is anchored to the draw-works and a deadline is anchored to an anchorage member. A derrick supports a drill string in conjunction with the fastline and deadline. A bit weight sensor produces a first signal proportional to the tension in the deadline, and a device is provided which produces a second signal proportional to the rate of change of tension in the deadline. The bit weight is varied by a control means in accordance with the rst signal. When the second signal reaches a maximum value, it is applied to the control means in such a Way as to maintain the first signal substantially at the then existing level while drilling continues.

This invention relates to methods and apparatus for use in drilling deep boreholes in the ground, whether of the rotary tubular drill string kind or of the kind having a non-rotary tubular drill string attached to a motor adjacent the drill bit. Such a motor may be a hydraulic turbine.

During drilling it is necessary to maintain the drill string above the drill collars in tension. It is also necessary to maintain as far as possible the appropriate weight on the drill bit so that it effectively penetrates and fractures the particular formation then being drilled. A measure of the effectiveness of the drilling operation is the rate of penetration of the bit, but that is dependent on a number of factors such as the drilling fluid, the design, current condition and rotational speed of the bit, and also the force with which the bit is applied against the bottom of the borehole, i.e. the bit Weight. Of these factors, the bit weight is the most critical and is contributed mostly by the drill collars.

It is normal to provide a bit weight indicator which is operated from the deadline. The indicator gives a maximum reading with a hanging bit and a minimum reading with the bit on the bottom of the borehole and no tension in the drill string. An intermediate reading is given during normal drilling. During drilling and watching the indicator, the drillei uses the brake of the draw-works winding drum to obtain the desired bit weight. As the bit penetrates downwards into the formation, the driller between adding sections of drill pipe operates the brake to provide a controlled pay-oftr of the fast line in an attempt to maintain the correct bit weight for optimum penetration of the formation being drilled. Since the optimum penetration for various kinds of formation will demand different bit weights, it is clear that the above method of operation involves a large element of guess-work based on the experience of the driller.

According to one aspect of the present invention, apparatus for use in drilling boreholes including draw-works having a braking means, a fastline anchored to the drawworks, a deadline anchored to an anchorage member, a derrick for supporting the drill string in conjunction with the fastline and deadline, a bit weight senser operated by the tension in the deadline for producing a signal proportional to such tension, is provided with a device for meas- 3,461,978 Patented Aug. 19, 1969 ice uring the rate of change of tension in the deadline and for producing a signal proportional to such rate of change of tension.

Such a signal may operate a visual indicator or operate means for automatically controlling the borehole drilling apparatus.

According to another aspect of the invention a method of borehole drilling, using such apparatus, comprises the steps whilst drilling of:

(a) Applying a high bit weight in relation to the prevailing drilling conditions,

(b) Drilling-off with the draw-works brake applied,

(c) Noting the hit weight registered by the bit weight senser when the device for measuring indicates a maximum rate of change of tension in the deadline, and

(d) Thereafter operating the brake to maintain that value registered by the bit weight senser while drilling continues.

The method of borehole drilling may be performed by an operator in conjunction with visual indication of bit weight and of rate of change of tension in the deadline, that is, of rate of change of bit weight, or it can be performed automatically with the bit weight and rate of change signals being fed into automatic control apparatus.

Preferably the device for measuring rate of change of tension in the deadline includes a frame having pulleys for engagement with the deadline, and a member, also engageable with the deadline but capable of movement relative to the frame when changes of tension occur in the deadline. This relative movement causes a transducer to deliver signals proportional to the rate of change of tension in the deadline.

Alternatively the device consists of a lever attached to a drum to which the deadline is anchored, the drum being capable of limited rotation as the tension in the deadline changes. A transducer is mounted adjacent the lever and such limited rotation causes the transducer to deliver the required signals.

By way of example various of apparatus according to the invention will now be described with reference to the accompanying drawings, in which:

FIGURE 1 is a diagram of apparatus for deep borehole drilling;

FIGURE 2 is, on a larger scale, a side elevation of one form of device for measuring the rate of change of tension in a deadline, the device being shown attached to the deadline and including an output signal circuit;

FIGURE 3 is an elevation at right angles to FIGURE 2 as seen in the direction of the arrow D;

FIGURE 4 is a semi-diagrammatic view of a deadline anchorage including a device for measuring and displaying an indication of rate of change of tension in a deadline;

FIGURE 5 is an isometric view of an indication means; and

FIGURE 6 is a block diagram of an automatic drilling control system.

Referring more especially to FIGURE 1, a stationary drilling derrick 10 and associated equipment is shown in position above a borehole within which hangs a rotary drill string including drill collars 12 and drill bit 13. The drill string above the drill collars comprises a number of joined sections of tubular drill pipe 14 terminating in a kelly 15, followed by a swivel 16, a hook 17 and a travelling 4block 18 suspended by a drilling -line 19, from a crown block 20. The latter is supported at the top of the derrick 10. One end of the `line 19, namely the fast line 19a, is taken to the draw-works 22 which contain the motor or motors for operating the drill string.

The draw-works 22 include a drum 60, to which the cfast Iline 19a is anchored, controlled by a brake shown generally at 61. The brake comprises a drum 62 around which is wrapped a brake band 63 capable of being forced tightly against the drum 62 by means of lever 64 to lock or to control the rate of paying-off the fast line 19a from the drum 60. The drum 60 is also used for winding-in the fast line 19a when desired. The, or a, drawworks motor also drives a rotary table 23 which in turn transmits the drive to the kelly 15 which is square in outer section. A hose 24 forms part of a supply system for conveying `drilling fluid to the drill pipe sections 14. The other end of the drilling line is secured to an anchorage member 25 including a winding-on drum 66. The portion 26 of the line which extends between the anchorage member 25 and the top of the crown block is called the deadline. A bit weight senser 65 adjacent to the member 25 is clamped to the deadline 26 and operates a remote indicator 27. Above the bit weight senser 65 and also clamped to the deadline is a sensing device 28 for measuring the rate of change of tension in the deadline. The sensor 28 operates a remote visual indicator 29.

Referring to FIGURES 2 and 3, a frame 30 which is secured by bolts 31 to a central support 32 mounts at its ends a pair of jockey-pulleys 33. A fairlead block 34 is slidable on a pair of bolts 35- at right angles to the support 32. The bolts 35 including their clamping nuts 36 clamp a housing 37 to the rear face 0f the block 34, the housing engaging a boss 38 on the block to which it is sealed by an O-ring 39. The housing 37 contains a stack of piezoelectric discs 40 which is electrically connected through insulating and sealing grommets 41 to circuitry housed in an adjacent box 42. The stack of piezo-electric discs 40 is clamped between an end wall of the housing 37 and the boss 38, the arrangement being such that the rear face of the block 34 is spaced from the adjacent end wall of the housing 37 by the discs 40. The deadline 26 is clamped between the jockey-pulleys 33 and the convex face of the block 34 by means of nuts 43a so as to cause a kink in the deadline, e.g. of between half and one diameter of the line.

The circuitry in box 42 comprises an amplifier input lead 43, a bias lead 44, a device 45 for damping out misleading signals which may arise from transient disturbances, e.g. pumping pulsations in the drilling fluid or wind forces on the derrick, an amplifier 46, and a device 47 including a diode and resistor which are shunted across power supply lines 48. The device 47 produces suicient voltage at the input to the amplifier 46 to balance the base-to-emitter diode voltage of the input transistor of the amplifier. The amplifier output is line 49. A box 50 houses the gauge 29, a battery 51 and a manually operated switch 52.

When the deadline is under tension, the block 34 is urged against the stack of discs 40. If tension in the deadline is increasing, the latter tends to straighten and urge the block 34 harder against the stack of discs 40. The resulting increasing compressive load on the discs causes them to produce an electrical charge proportional to the load and hence an electrical current in the resistance 45a which is proportional to the rate of change in their loading and thus to the rate of change of tension in the deadline.

The impedance of the amplier being high, almost all of this current flows through the resistance 45a, thus resulting in a voltage drop across the resistance which must be proportional to the rate of change of tension. This voltage is smoothed of misleading signals by the device 45 which is in fact a capacitor.

As an alternative arrangement, the sensing device for measuring rate of change of tension in the deadline 26 may 'be incorporated in thedeadline anchorage member 25. This alternative is illustrated in FIGURE 4. It comprises a lever 67 rigidly attached to the drum 66, and a transducer 68, for example a fluid pressure responsive member such as a diaphragm air pump, mounted between the lever 67 and a fixed part of the anchorage member 25. The transducer 68 is in communication, through the pipe 69, to a capsule 70 adjacent to the remote indicator 29a, one end of the capsule being connected via a linkage 71 so as to rotate a quadrant 72 on which gear teeth are formed. A gear wheel 73 meshes with this quadrant to rotate an indicator arm 74. At a convenient point along the length of pipe 69 is provided a capillary vent giving a controlled leakage to atmosphere and illustrated at reference numeral 75.

When the deadline 26 is subjected to a change in tension the lever 67 is urged towards or away from the fixed part of the anchorage 25 so that a change in the volume of the fluid pressure responsive member 68 transmits a change in fluid pressure via line 69 to the capsule 70 which expands or contracts accordingly. Due to the controlled leakage at capillary 75 the arm 74 records only rate of change of tension in the deadline.

The bit weight senser 65 which may be of any suitable kind, is in this example clamped to the deadline so as to form a kink therein. As the load on the deadline increases, the deadline tends to straighten and thereby actuate the visual indicator 27 which is calibrated in bit weight units. The calibration takes account of the fact that the bit weight is the weight fo the drill string minus the force applied beween the blocks 18, 20 by the tension in the drilling line.

It will be seen that the drill string from the bit to the kelly, the swivel, hook and blocks and finally the derrick itself may be regarded as forming together a spring systern. With the draw-works winding drum for the fast line locked, bit penetration during drilling involves elongation of the spring system, which involves increase in spring tension, while the bit weight falls to the same extent as the spring tension increases. The rate of increase in spring tension is directly proportional to the downwards penetration rate of the bit.

The invention may be used in the following manner. While drilling and watching the bit weight indicator 27, the driller applies a high bit weight, i.e. higher than is likely to be optimum in the prevailing conditions, which include depth of borehole, type of formation and bit diameter. He then locks the brake to prevent further pay-off of the fast line from the winding drum, and continues drilling. Assuming a sufliciently high bit weight has been applied, the penetration rate of the bit will rise to a maximum figure when the bit weight has fallen to an optimum value. Thereafter the penetration rate will commence to fall as bit weight further decreases. When the penetration rate as indicated at 29 or 29a has reached a maximum figure, the driller checks the bit weight then shown by the indicator 27, and thereafter continues drilling while operating the brake to obtain and maintain as far as possible the 'bit weight at this value, corresponding to the indicated maximum penetration rate of the bit.

At appropriate intervals, depending on such variables as change in formation being drilled, and bit wear, the driller `will repeat this procedure, making such changes if any in the bit weight as the use of both indicators suggests.

In this manner the invention reduces the amount of guesswork involved in seeking to maintain the optimum bit penetration rate under various conditions of drilling.'

The information supplied to the two indicators 27, 29 or 29a may, to facilitate observation by the driller, be fed instead to a single instrument 76 illustrated in FIG- URE 5. It is constructed as follows. A spindle 77 operated by rate of change signals is mounted coaxially with a sleeve 78 operated by bit weight signals. The sleeve 78 carries an arm 79 fixed to the sleeve. The spindle 77 carries an arm 80 which has a friction grip on the spindle. A fixed member 81 also coaxial with the spindle 77 carries the hub 82 of a pointer 83 which has a friction grip in the fixed member. The lixed member 81 supports a dial 84 against which the information presented by arms 79, 86 and pointer 83 can be read oli. The arm 79 is mounted behind the viewing face of the dial 84 and is cranked to extend through an annular slot 85 in the face of the dial. The grip of the hub 82 on the xed member 81, expressed as torque necessary to produce slipping, is less than the grip of the arm -80 on the spindle 77. The arms 79, 80 and pointer =83 have portions lying in a common plane perpendicular to the axis of the instrument. Looking along the axis, from the front of the instrument, that is generally from the right of FIGURE 5, the pointer 83 extends upwards, with the arm 79 lying Ito its right and the arm 80 to its left. The arm 79 moves clockwise as bit weight decreases. Initially the arm 80, pointer 83, and arm 79 are all close togehter. The spindle 77 turns clockwise so long as the rate of change of bit weight is rising. Thereby it exerts a clockwise slipping torque on the arm 80 which engages the pointer 83 and carries it clockwise in engagement with the arm 79. When the rate of change passes a maximum, the movement of the spindle 77 reverses to anticlockwise. The arm 80 moves away from the pointer 83 and leaves the pointer stationary, while the arm 79 continues to move clockwise (so long as the brake is applied to the fastline). The stationary position attained by the pointer 83 indicates the value of bit weight for maximum rate of vchange of tension in the deadline. The arm 79 and the pointer 83 are arranged to move over a scale on the dial 84 graduated in bit weight units, ranging from high bit weight to low bit weigh-t. The arm 80 is arranged to move over a part of the dial graduated in rate of change of bit weight units which units are, of course, proportional to the rate of change of tension inthe deadline.

As an alternative to an operator observing an indicator and controlling the brake, there may be an automatic drilling control system which reecives signals from the rate of change of tension senser 28, or that situated in the anchorage 2S, and from the bit Weight senser 65, and which rst performs the sequence of operations to determine optimum bit weight and then automatically regulates the pay-off of the fast line to maintain the appropriate bit Weight for maximum bit penetration rate.

A block diagram of such a control system is illustrated in FIGURE 6. A senser, for example that referenced 28 in FIGURE 1 passes a rate of change of tension signal (i.e. proportional to rate of change of bit Weight) along line 86, to an indicator 29 and to a dilerentiating means -87 which gives an output signal along the line 88 When the rate of change of tension signal reaches a maximum. After delivering this signal the differentiating device requires to be reset before it will give a further out-put signal. Resetting is arranged by a timing device 89 which at certain intervals passes a resetting signal along the line 90 to the diiferentiating device 87. Line -88 and a further line 91 from the timing device 89 are connected to a control means 92 which controls the action of the drawworks brake in a manner to be described. The control device 92 is also provided with a signal along the line 93 from the bit weight senser y65. The signal is also passed to, for example, the indicator 27.

The system functions in the following manner. During drilling, the timing device 89 causes a signal to be passed along 91 to the control device 92 to cause the brake pressure to be relaxed and allow the bit weight to rise to a predetermined maximum which is higher than is likely to be optimum in the prevailing drilling conditions whereupon the consequent rise in signal strength from the senser 65 causes the brake to become locked to prevent.

further pay-olf of the fast line from the winding drum. A further signal is passed along the line 90 to reset the differentiating device 87 should this be necessary. Drilling is continued and a rate of change of bit weight signal and a bit weight signal are provided by sensers 28 and 65 respectively. When the rate of change signal reaches a maximum (other than a misleading one due to transient disturbances), that is when the bit penetration rate is optimum, the differentiating device 87 passes a signal along line l88 to the control means 92, which at the instant of receiving this signal registers the bit 'weight signal at its instantaneous value and thereafter operates the draw- Works brake to maintain the bit weight signal being received along the line 93 at the stored value. At a preset interval of time the timing device 89 causes the differentiating device 87 to be reset and the draw-works brake to be relaxed to allow bit weight to again rise to the predetermined maximum so that the cycle is repeated.

In a modication, not illustrated, the amplier of the senser 28 is connected to an instrument which also receives a signal indicative of pay-off from the winding drum. The instrument combines the twosets of signals and provides a continuous indication of bit penetration rate under varying conditions of drilling.

The order of quantities involved in operation according to the present invention is indicated by the following example: in one particular apparatus as shown in the accompanying drawings, a change of 24,000 lbs. in -bit weight is represen'ted by a 3,000 lb. change in loading on the stack 40. A 24,000 lb. change in bit weight over 500 secs. will result in a half-volt input signal to box 42, with a very small current.

I claim:

1. Apparatus for use in drilling boreholes including draw-Works having a braking means, a fastline anchored to the draw-works, a deadline anchored to an archorage member, a derrick for supporting a drill string in conjunction with the fastline and deadline, a bit weight senser operated by the tension in the deadline for producing a signal proportional to such tension, and a device for measuring the rate of change of tension in the deadline and for producing a signal proportional to such rate of change of tension.

2. Apparatus according to claim 1 in which the device for measuring the rate of change of tension in the deadline is clamped to the deadline.

3. Apparatus according to claim 1, in which the signal produced by the bit weight senser is passed to a control means for varying 'the bit weight and in which the signal produced by the rate of change of tension measuring device is passed to a dilferentiating means arranged to produce an output signal when the signal produced by the rate of change of tension measuring device reaches a maximum value, the output signal being passed to the control means, the control means adapted to register the value of the signal produced by the bit weight indicator at the instant of receiving the output signal from the differentiating means and thereafter to maintain the signal produced by the bit weight senser substantially at the level registered while drilling continues.

4. Apparatus according to claim 3, in which a timing means is adapted to provide a iirst signal to the control means to allow the bit Weight to increase, a second signal to the control means to prevent further increase of bit weight and a signal to reset the dilferentia'ting means.

5. A method of borehole drilling using apparatus including draw-works having a braking means, a fastline anchored to the draw-works, a deadline anchored to an anchorage member, a derrick for supporting a drill string in conjunction with the fastline and deadline, a bit weight senser operated by the tension in the deadline for producing a signal proportional to such tension, and a device for measuring the rate of change of tension in the deadline and for producing a signal proportional to such rate of change of tension, comprising the steps whilst drilling of:

(a) applying a high bit weight in relation to the prevailing drilling conditions,

(b) drilling-off with the draw-works brake applied,

(c) noting the bit weight registered by the bit weight senser, when the device for measuring indicates a maximum rate of change of tension in the deadline, and

(d) thereafter operating the brake to maintain that value registered by the bit weight senser while drilling conftinues.

6. A method of borehole drilling using apparatus including draw-works having a braking means, a fast-line anchored to the draw-Works, a deadline anchored to an anchorage member, a derrick for supporting a drill string in conjunction with the fastline and deadline, a bit weight senser operated by the tension in the deadline for producing a signal proportional to such tension, and a device for measuring the rate of change of tension in the deadline and for producing a signal proportional to such rate of change of tension, in which apparatus the signal produced by the bit weight senser is passed to a control means for varying the bit Weight and in which the signal produced by the rate of change of the tension measuring device is passed to a differentiating means arranged to produce an output signal when the signal produced by the rate of change of the tension measuring device reaches a maximum value, the output signal being passed to the control means, the control means adapted to register the value of the signal produced by the bit weight, indicator at the instant of receiving the output signal from the differentiating means and thereafter to maintain the signal produced by the bit weight senser substantially at the level registered while drilling continues, comprising the steps, in automatic sequence, of z (a) applying a high bit weight in relation to the prevail- 2 ing drilling conditions,

(b) applying the draw-Works brake and drilling off,

(c) diierentiating the signal produced by the rate of change of tension device,

(d) producing a further signal when the rate of change signal reaches a maximum value,

(e) registering the value of the signal produced by the bit Weight senser at the instant of production of the further signal, and

(f) thereafter controlling the bit weight to maintain 10 substantially the registered value of the signal produced by the bit Weight senser while drilling continues.

References Cited 15 UNITED STATES PATENTS 2,327,505 8/1943 Conrad et al. 173-4 2,455,917 12/1948 Crake 254-173 2,688,871 9/1954 Lubinski 73-151.5 2,931,628 5/1960 Simmonds et al. 254-173 CHARLES E. OCONNELL, Primary Examiner R. E. FAVREAU, Assistant Examiner 5 Us. c1. xn. 

